Inflatable restraint systems or “airbag” systems have become a standard feature in many new vehicles. These systems have made significant contributions to automobile safety, however, as with the addition of any standard feature, they increase the cost, manufacturing complexity and weight of the vehicles. Technological advances addressing these concerns are typically welcomed by the industry. In particular, the gas generator or inflator used in many occupant restraint systems tends to be the heaviest, most complex component. Thus, trimming weight and assembly time by simplifying the design and manufacturing of airbag inflators, without sacrificing function, has long been a goal of automotive engineers.
The manufacturing steps necessary to assemble the various body components of the inflator are of particular interest to designers seeking to lower manufacturing costs, weight and design complexity. The inflator body components are traditionally welded together, either by conventional welding techniques or with laser welds. For example, in driver-side airbag systems, the inflator often has a disc-shape, and is formed by attaching one or more body cups with circumferential welds. An initiator assembly, or igniter, is also typically welded to one of the body components with a circumferential weld. The various welding processes typically require relatively expensive manufacturing equipment, and can require substantial processing time. Various improvements in the techniques and processes for welding inflator components have been made over the years; however, welding can continue to present challenges. Relatively thick, heavy walls and internal support members in the interior of the gas generator housing may be necessary to ensure that the components can be successfully, safely welded together. Trained operators and relatively expensive equipment are often necessary in the welding process, and for performing post-processing inspections, such as X-ray inspection of the individual welds. In addition, the use of lasers or other welding devices around combustible materials such as the gas generant materials used in inflators presents inherent safety problems.
In response to the concerns associated with welding, various attempts have been made to develop inflator systems capable of weld-less assembly. One example is described in U.S. Pat. No. 4,923,212 to Cuevas. Cuevas discloses an inflator design wherein magnetic fields are used to crimp or form a metal ring about multiple inflator body components. Cuevas requires the use of relatively expensive, complex magnaforming equipment. Moreover, Cuevas exhibits a relatively complex design in that a securing ring is used to complete the assembly.